This invention relates generally to vacuum pickup heads, and more particularly to a vacuum pickup head which automatically aligns specimens, such as integrated circuit chips, in predetermined planar orientation and x-y displacement, and returns the specimen to its original orientation and location upon release thereof.
There exist a number of problems with pick and place units, such as those which are used to pick up integrated circuits at a first location and transport same to a second location, illustratively a test socket site. Generally, the integrated circuits are arranged on one or more trays which usually are formed of a conductive plastic material. However, the plastic trays are subject to distortion, such as warpage, which causes the integrated circuit chips thereon to be arranged at various angular orientations with respect to a horizontal plane. Such non-horizontal orientations reduces the probability that a vacuum-tight engagement will occur between a conventional vacuum pickup head and the integrated circuit thereby resulting in chips not being picked up, chips being dropped, machine jamming, and generally a reduction in throughput.
In addition to the foregoing, there is a need to displace an integrated circuit chip, once it is picked up, such that it can be deposited accurately at a predetermined location after transportation. In the case where the predetermined location contains a test socket which has very small tolerances, illustratively on the order to thousandths of an inch, it is crucial that the chip be precisely aligned to avoid bending of the electrical leads. If it is desired, after testing, to return the chip to the tray from which it was picked up, or some other tray, the chip, having been displaced to achieve the precise alignment with the test socket, will not be returned to the precise original location, resulting in chips being misplaced on the tray. Again, this would require intervention by a human operator, raising operating costs and reducing net throughput.
It is, therefore, an object of this invention to provide a vacuum pickup arrangement which achieves a reliable vacuum engagement with specimens which are not precisely in planar registration with one another.
It is another object of this invention to provide a vacuum pickup head which maintains vacuum engagement with a specimen, not withstanding that the specimen is displaced in the x and/or y direction to achieve a precise orientation at a location to which the specimen is transported.
It is also an object of this invention to provide a vacuum pickup arrangement which, after a picked up specimen is displaced laterally, restores the specimen to its original location where it was originally picked up.